1. Field of the Invention
The present invention is directed to an apparatus for treating bone pathologies with acoustic energy, administered by acoustic waves.
2. Description of the Prior Art
Recent experiments have shown that the healing process for certain bone pathologies can be accelerated, beneficially influenced, or initiated by applying acoustic energy, particularly focused shockwaves, to a bone region. Such treatment is described in PCT Application WO88/09190, corresponding to U.S. Pat. No. 4,979,501. As described therein, such treatment has heretofore been implemented using lithotriptors, also known as extracorporeal shockwave devices (ESWD). These are shockwave therapy devices which are normally used for the purpose of treating stone pathologies, for example, nephrolithiasis, with focused shockwaves.
In treating bone pathologies, particularly pathologies in a region of the long bones of the extremities, with focused shockwaves, it is necessary, while retaining the acoustic coupling of the therapy apparatus with the body part to be treated, to execute a relative motion between the focus of the acoustic waves and the body part to be treated, such that the focus of the acoustic waves is moved along the zone requiring treatment. When treating the fracture of a long bone, for example, this means that the focus of the acoustic waves must be moved along the fracture break. In order to maintain the stress to the patient, resulting from the application of acoustic energy, at as low a level as possible, it is preferable to irradiate the bone with acoustic shockwaves which proceed to the treatment location along a direct path. This means that the acoustic waves, for example, should not be required to initially propagate through a bone wall disposed diametrically opposite the location to be treated, because this would result in excessively high acoustic losses. It is thus necessary to move the therapy apparatus around the body part to be treated, for example, in an approximately circular motion. A further problem is that the distance of the bone from the surface of the body part to be treated is not constant, so that the spacing of the focus from the surface of the body part must be constantly adjusted, by setting different spacings, during the displacement of the focus and the body part containing the bone requiring treatment relative to each other.
These requirement are extremely difficult to satisfy with a lithotriptor, because the patient support as well as its adjustment possibilities are adapted for a different type of treatment. Moreover, the adjustment possibilities of the shockwave generator and of the locating system are designed for charging the patient with shockwaves in the trunk region, and once alignment of the patient and the shockwave generator relative to each other has been achieved, the located position is essentially retained, and is varied only for the purpose of making corrections and small adjustments as may become necessary because of changes in the position of the calculus occurring during the treatment. Therefore, treatment of bone pathologies can only be implemented in a complicated fashion using conventional lithotriptors, and thus involves risks for the patient due to the danger of incorrect operation of the treatment apparatus as well as due to locating errors.